Downhole tool with external housing torque transfer

ABSTRACT

A downhole tool comprises a first connector sub coupled to an outer housing. A mandrel is disposed in the outer housing and is coupled to a mandrel. The second connector sub is slidably engaged with the outer housing so that torque loads are transferred from the first connector sub to the second connector sub through the outer housing independently of the mandrel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Patent Application Ser. No. 61/588,887, titled Downhole Tool with External Housing Torque Transfer, which was filed Jan. 20, 2012, which is hereby incorporated by reference in their entirety into the present application, to the extent that it is not inconsistent with the present application.

BACKGROUND

This disclosure relates generally to a downhole tool for use in a wellbore. More particularly, this disclosure relates to a downhole tool that can handle increased axial and rotational loads.

A jar is a downhole tool used to deliver an axial impact load. Jars are often utilized to apply an axial impact load when the drill string becomes stuck in the wellbore. When a drill string becomes stuck in a wellbore, applying or releasing tension at the surface stretches or compresses the drill string causing energy to be stored in the drill string. A jar operates by providing a mechanism that allows for the energy stored in the drill string to be quickly released and applied to the drill string as an axial impact load.

Conventional jars operate by selectively constraining the relative axial movement between an outer housing and an inner mandrel. For purposes of this description, the inner mandrel is coupled to the stuck portion of the drill string and remains fixed while the outer housing moves axially in response to tension in the drill string and activation of the jar. It is understood that in other embodiments, the operation of the components is reversed and the outer housing is fixed while the inner mandrel moves axially.

As previous mentioned, when a tool becomes stuck, tension is applied to or released from the drill string to store energy in the drill string. Once the desired load is applied, the jar is “fired,” and the outer housing is allowed to translate axially relative to the inner mandrel and apply an impact load that is transferred to the stuck portions of the drill string. Both mechanical and hydraulic jars are available. Hydraulic jars utilize hydraulic fluid to constrain the movement of the outer housing relative to the mandrel. Mechanical jars utilize mechanical components, such as springs or latches, to constrain the movement of the outer housing relative to the mandrel.

Jars may be may be bi-directional, meaning they are capable of delivering an impact blow in both the uphole and downhole directions. Alternatively, a jar may be uni-directional, meaning it is designed for and is capable of delivering an impact blow in either the uphole or downhole direction, but not both. Regardless, the common feature of each is that stored energy, created by stretching or compressing the drill string, is used to accelerate the outer housing of the hydraulic jar to deliver an axial impact blow to the mandrel. Moreover, the higher the load applied to the outer housing, the faster the acceleration of the outer housing and the greater the impact force delivered to the mandrel.

Jars may be used with a variety of wellbore operations, including drilling, fishing, and milling operations. Each of these operations requires a different set of performance criteria. In order to meet a wide variety of performance criteria, jars are available in a wide range of configurations. Jars can also be designed to work with drill pipe and on coiled tubing.

Providing jars for use with coiled tubing presents a number of working constraints to conventional tool design. First of all, due to the limited size of the coiled tubing, limited compressive loads can be placed on the tubing by the rig operator. Essentially, this means that downhole tools which require compressive force to operate, such as a jar, must be capable of operating with the limited compressive load capability of coiled tubing. Further, coiled tubing operations often limit the outside diameter of the jar and require a relative large inside diameter to allow the passage of fluids and certain tools through the jar.

In addition, in coiled tubing application the overall length of the downhole tool becomes significant since there is limited space at the surface to accommodate the bottom hole assembly (BHA). A typical BHA used for drilling or milling might include a drill bit, a mud motor that provides torque to the drill bit, a jar, a steering tool, and other tools and components depending on the operation being performed. Therefore, the overall length of the jar itself becomes particularly significant.

The operating envelope for coiled tubing, both in well depth and conditions, is also expanding and further increasing the performance requirements of the entire BHA, including the jar. Higher torques applied by the mud motor and higher axial loads due to longer, larger coiled tubing strings increase the loads applied to and by the jar.

Thus, there is a continuing need in the art for jars that are able to meet increased performance requirements as compared to the prior art.

BRIEF SUMMARY OF THE DISCLOSURE

In certain embodiments, a downhole tool comprises a first connector sub coupled to an outer housing. A mandrel is disposed in the outer housing and is coupled to a mandrel. The second connector sub is slidably engaged with the outer housing so that torque loads are transferred from the first connector sub to the second connector sub through the outer housing independently of the mandrel.

In certain embodiments, a jar assembly comprises a first connector sub coupled to an outer housing. A mandrel is disposed in the housing. A jar mechanism is disposed in an annulus between the outer housing and the mandrel and selectively restricts relative axial movement between the outer housing and the mandrel. A second connector sub is coupled to the mandrel and is slidably engaged with the outer housing.

In certain embodiments, a method of operating a downhole tool comprises coupling an outer housing to a first connector sub and coupling a mandrel to a second connector sub. The mandrel is disposes within the outer housing. The outer housing is slidably engaged with the second connector sub so that torque loads are transferred from the first connector sub to the second connector sub through the outer housing independently of the mandrel.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more detailed description of the embodiments of the present disclosure, reference will now be made to the accompanying drawings.

FIGS. 1A-C are sectional views of a jar assembly shown in a closed position;

FIGS. 2A-B are partial sectional views of a portion of the jar assembly of FIG. 1.

FIGS. 3A-C are sectional views of the jar assembly of FIG. 1, shown in the full open position.

FIG. 4 is a partial isometric view of a portion of the jar assembly of FIG. 1.

DETAILED DESCRIPTION

It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.

Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term “or” is intended to encompass both exclusive and inclusive cases, i.e., “A or B” is intended to be synonymous with “at least one of A and B,” unless otherwise expressly specified herein. For the purposes of this application, the term “real-time” means without significant delay.

The present disclosure uses the directional and position terms such as “upper,” “up,” “lower,” and “down” as references only with respect to other parts in the assembly and their relative positions in the figures presented herewith. It is understood that the embodiments shown and described herein can be operated in the orientations shown or can be reversed without altering the performance of the components.

Referring initially to FIGS. 1A-C, jar assembly 100 includes an upper connector sub 102 that is coupled to an outer housing 104. The outer housing 104 is formed from a pressure body 132 that is coupled to a torque body 134 by threads 133. A lower connector sub 106 is slidably engaged with the torque body 134 so that the lower connector sub 106 can move axially relative to the torque body 134 but is rotationally coupled to torque body 134. A mandrel 108, including an upper mandrel 110 and a lower mandrel 112, is fixably coupled to the lower connector sub 106 and extends upward through the outer housing 104 and into the upper connector sub 102. Upper seal 114 and lower seal 116 define a pressure chamber 118 defined by the outer housing 104 and the mandrel 108. In operation, the pressure chamber 118 is filled with a substantially incompressible fluid, such as a hydraulic fluid.

Up seal body 120, down seal body 122, and cones 124 are disposed within the pressure chamber 118 in the annulus between the mandrel 108 and the outer housing 104. Each seal body 120, 122 sealingly engages the outer surface of the mandrel 108 via seals 126 and includes a metering groove 128 on a surface 129 that abuts the cones 124. Pressure body 132 includes a reduced diameter portion, or detent 130 along its inner surface that is sized to sealingly engage the outer diameter of cones 124. As will be discussed in detail to follow, the up seal body 120, down seal body 122, cones 124, and detent 130 form the jar mechanism that restricts the movement of hydraulic fluid through the pressure chamber 118 so as to restrain axial movement of the mandrel 108 relative to the pressure body 132 and fire the jar.

By way of example, the operation of jar assembly 100 will be described with the jar assembly being run in the closed position shown in FIGS. 1A-C and being used to apply an upward jarring force to a stuck BHA. The lower connector sub 106 is coupled to a BHA (not shown) and the upper connector sub 102 is coupled to the drill string (not shown) that extends to the surface. In order to energize the jar assembly 100, a tension load is applied to the upper connector sub 102 by pulling on the drill string from the surface. Because the lower connector sub 106 is coupled to the stuck BHA, applying a tension load to the upper connector sub 102 will cause the upper connector sub 102 and the outer housing 104 to move upward relative to the lower connector sub 106 and mandrel 108.

As shown in FIG. 2A and 2B, the outer housing 104 moves upward relative to the mandrel 108 until up seal body 120 contacts shoulder 136 of upper mandrel 110 and cone 124 engages the detent 130. The inner diameter of up seal body 120 is sealingly engaged with the mandrel 108 and the outer diameter of the cone 124 is sealingly engaged with the detent 130, so that flow 200 of hydraulic fluid is directed through metering groove 128. Because the hydraulic fluid is primarily incompressible, the axial movement of the mandrel 108 relative to the outer housing 104 is restricted. As fluid moves through the metering groove 128, the outer housing 104 will continue to move upward relative to the mandrel 108.

Limiting the flow of fluid through the metering groove 128 allows the stored energy in the drill string to be increased. In order to control the flow of fluid and allow the desired load to be generated, metering groove 128 may be a linear groove, a spiral groove, or some other configuration that allows a controlled amount of fluid to flow between the face of the cone 124 and the seal body 120. Certain groove configurations are shown in U.S. Pat. Nos. 5,906,239 and 7,814,995, both of which are incorporated by reference herein for all purposes.

As tension is applied to the drill string and the BHA remains stuck, the cone 124 slowly moves along the detent 130 as fluid is allowed to pass through the metering groove 128. As the cone 124 reaches the end 202 of the detent 130, the seal between the cone and the detent is broken. Fluid flow across the detent 130 is no longer restricted and the jar assembly 100 is fired. The outer housing 104 can now move freely relative to the mandrel 108 and the stored tension load in the drill string accelerates the outer housing 104 upwards until the upper end 302 of the torque body 134 impacts the shoulder 304 of the mandrel 108, as is shown in FIGS. 3A-3C. The impact between the torque body 134 and the shoulder 304 transfers the axial impact load into the lower connector sub 106 and the connected BHA.

As the outer housing 104 moves upward, torque body 134 also moves upward relative to the lower connector sub 106. The torque body 134 is slidably coupled to the lower connector sub 106 though any connection that allows relative axial movement but transmits torque loads. For example, the torque body 134 may be coupled to the lower connector sub 106 though a plurality of longitudinal splines 308 (see FIG. 4) on the lower connector sub 106 that engage corresponding grooves 306 on the inner surface of the torque body 134. The outer housing 104 may also include one or more fluid ports 310 through the wall of the torque body 134. Fluid ports 310 provide fluid communication that allows wellbore fluids and debris to move into or out of the annulus 312 formed between the torque body 134 of the outer housing 104 and the lower connector sub 106.

In other embodiments, the lower connector sub 106 and the torque body 134 may be coupled by splines having any desired shape, number, or configuration. Other torque-transferring couplings may also be used including, but not limited to, pin in slot couplings and faceted tubulars. By extending the torque body 134 into slidable engagement with the lower connector sub 106, any residual torque stored in the stuck BHA is transferred from the lower connector sub 106 to the upper connector sub 102 via the torque body 134 and pressure body 132, thus bypassing the mandrel 108. In this manner, the stresses on the mandrel 108 are reduced because the mandrel 108 is effectively isolated from any torque loads transmitted through the jar assembly 100.

Isolating the mandrel 108 from torque loads may be especially critical when the jar assembly 100 is used with a BHA that includes mud motor. Often, when a BHA including a mud motor becomes stuck, the mud motor stalls at its maximum torque condition. Therefore, when the BHA becomes unstuck, a high torque load is immediately applied to the drill string. As the performance of mud motors increases the potential for damage to other components increases. By isolating the mandrel 108 of jar assembly 100 from that torque load, higher axial loads can safely be applied to the mandrel 108.

Telescopically extending the torque body 134 over the outside of the lower connector sub 106 also allows for the overall length of the jar assembly 100 to be reduced. The overall length of the jar assembly 100 may also be reduced by optimizing the travel of the jar during firing. Once the cone 124 disengages the detent, the outer housing 104 accelerates until it impacts the mandrel 108. By controlling the length of the outer housing 104 and the size and placement of the detent 130, the jar assembly can be optimized by placing the impact point at a distance where the impact force would be maximized. This distance is dependent on the drill string with which the jar assembly 100 would be used.

The jar assembly 100 can also be used to apply a downward jarring force to the lower connector sub 106. With the jar assembly 100 in an open position, as is shown in FIGS. 3A-3C, the upper connector sub 102 and outer housing 104 are lowered relative to the lower connector sub 106, which is fixed in place. The outer housing 104 moves downward relative to the mandrel 108 until down seal body 122 contacts the shoulder 304 of mandrel 108 and cone 124 engages the detent 130. The inner diameter of down seal body 120 is sealingly engaged with the mandrel 108 and the outer diameter of the cone 124 is sealingly engaged with the detent 130, so flow of hydraulic fluid is directed through metering groove 128 that restricts the flow of hydraulic fluid so that a compressive load can be applied by releasing tension from the drill string.

As the drill string is placed in compression and the BHA remains stuck, the cone 124 slowly moves along the detent 130 as fluid is allowed to pass through the metering groove 128. As the cone 124 reaches the end of the detent 130, the seal between the cone and the detent is broken and the axial movement of the outer housing 104 is no longer restricted. The compressive load in the drill string moves the outer housing 104 downwards until the lower end 314 of the torque body 134 impacts the shoulder 316 of the lower connector sub 106. The impact between the torque body 134 and the shoulder 316 transfers the axial impact load into the lower connector sub 106 and the connected BHA. As with an upward jar, any torque is transferred from the lower connector sub 106 to the upper connector sub 102 via the torque body 134 and pressure body 132, thus bypassing the mandrel 108.

The lower connector sub 106 and torque body 134 configurations shown herein can also be applied to other hydraulic and mechanical jar systems as well as other downhole tools. Isolating torque loads from axial impact loads and transferring these loads through two separate components reduces the stress applied to any single component and allows a downhole tool to handle higher axial loads and higher torque loads.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and description. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the disclosure to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure. 

What is claimed is:
 1. A downhole tool comprising: a first connector sub; an outer housing coupled to the first connector sub; a mandrel disposed in the outer housing; and a second connector sub coupled to the mandrel and slidably engaged with the outer housing, wherein torque loads are transferred from the first connector sub to the second connector sub through the outer housing independently of the mandrel.
 2. The downhole tool of claim 1, further comprising a jar mechanism disposed in an annulus between the outer housing and the mandrel, wherein the jar mechanism selectively restricts relative axial movement between the outer housing and the mandrel.
 3. The downhole tool of claim 2, wherein the jar mechanism further comprises: a seal body sealingly engaged with the mandrel; a cone operable to sealingly engage a portion of the outer housing; and a metering groove disposed between the seal body and the cone.
 4. The downhole tool of claim 3, wherein the cone sealingly engages a detent disposed on an inner surface of the outer housing.
 5. The downhole tool of claim 1, further comprising: a plurality of splines disposed on an outer surface of the second connector sub; and a plurality of grooves disposed on an inner surface of the outer housing and engaged with the plurality of splines.
 6. The downhole tool of claim 1, further comprising a plurality of ports that provide fluid communication across a wall of the outer housing into an annulus between the outer housing and the second connector sub.
 7. A jar assembly comprising: a first connector sub; an outer housing coupled to the first connector sub; a mandrel disposed in the housing; a jar mechanism disposed in an annulus between the outer housing and the mandrel, wherein the jar mechanism selectively restricts relative axial movement between the outer housing and the mandrel; and a second connector sub coupled to the mandrel and slidably engaged with the outer housing.
 8. The jar assembly of claim 7, wherein the jar mechanism further comprises: a seal body sealingly engaged with the mandrel; a cone operable to sealingly engage a portion of the outer housing; and a metering groove disposed between the seal body and the cone.
 9. The jar assembly of claim 8, wherein the cone sealingly engages a detent disposed on an inner surface of the outer housing.
 10. The jar assembly of claim 7, further comprising: a plurality of splines disposed on an outer surface of the second connector sub; and a plurality of grooves disposed on an inner surface of the outer housing and engaged with the plurality of splines.
 11. The jar assembly of claim 7, further comprising a plurality of ports that provide fluid communication across a wall of the outer housing into an annulus between the outer housing and the second connector sub.
 12. The jar assembly of claim 7, wherein the outer housing further comprises: a pressure body that is coupled to the first connector sub; and a torque body that is coupled to the pressure body and slidably engaged with the second connector sub.
 13. The jar assembly of claim 7, further comprising a shoulder disposed on the mandrel, wherein the shoulder is operable to contact the outer housing when the first connector sub moves away from the second connector sub.
 14. The jar assembly of claim 7, further comprising a shoulder disposed on the second connector sub, wherein the shoulder is operable to contact the outer housing when the first connector sub is moving toward the second connector sub.
 15. A method of operating a downhole tool comprising: coupling an outer housing to a first connector sub; coupling a mandrel to a second connector sub; disposing the mandrel within the outer housing; and slidably engaging the second connector sub with the outer housing so that torque loads are transferred from the first connector sub to the second connector sub through the outer housing independently of the mandrel.
 16. The method of claim 15, further comprising: disposing a jar mechanism in an annulus between the outer housing and the mandrel; and operating the jar mechanism so as to selectively restrict relative axial movement between the outer housing and the mandrel.
 17. The method of claim 16, wherein the jar mechanism uses hydraulic fluid to restrict relative axial movement between the outer housing and the mandrel.
 18. The method of claim 16, wherein operating the jar mechanism further comprises: sealingly engaging the mandrel with a seal body disposed within the annulus between the outer housing and the mandrel; and sealingly engaging the outer housing with a cone disposed adjacent to the seal body, wherein a metering groove restricts fluid flow between the seal body and the cone.
 19. The method of claim 15, wherein torque loads are transferred by a plurality of splines disposed on an outer surface of the second connector sub that are engaged with a plurality of grooves disposed on an inner surface of the outer housing.
 20. The method of claim 15, wherein at least a portion of the second connector sub is disposed within the outer housing. 